The role of α2-adrenoceptors in regulation of gastric motility has been well documented. However, only few data are available on the adrenoceptor subtype that mediates this effect. The purpose of the present work was to identify the α2-adrenoceptor subtype(s) responsible for the inhibition of gastric motor activity in isolated fundus strip of the mouse. It was shown that (i) the electrically evoked contraction of the gastric fundus strip of the mouse was inhibited by the non-selective α2- adrenoceptor stimulant clonidine (EC50: 0.019 ± 0.001 μM), the α2A-adrenoceptor subtype selective agonist oxymetazoline (EC50: 0.004 ± 0.001 μM) and the α2B- adrenoceptor subtype preferring ST-91 (EC50: 0.029 ± 0.004 μM), (ii) the inhibitory effect of clonidine (1 μM), oxymetazoline (0.1 μM) and ST-91 (1 μM) on the contractions of gastric fundus strip was reversed by the non-selective α2-adrenoceptor antagonist idazoxan and α2A-adrenoceptor antagonist BRL 44408, but not by the α2B/2C-adrenoceptor antagonist ARC-239. (iii) Clonidine and ST-91 inhibited the electrically induced gastric contractions in C57BL/6 wild type mice as well as in α2B- and α2C- adrenoceptor deficient mice in a concentration-dependent manner; however, neither of them was effective in α2A-deficient mice. As a conclusion, it was first demonstrated that the inhibitory effect of α2-adrenoceptor agonists on the gastric motor activity of isolated stomach strip of the mouse is mediated purely by α2A- adrenoceptors.
ASJC Scopus subject areas
- Cellular and Molecular Neuroscience
- Cell Biology